: Version 2.0 and above marks the "Enhanced Edition" of the game. This means the "piece" you are looking at includes significant quality-of-life updates, a revamped UI, and the integration of many fixes that weren't present at the 2021 launch.
If you are looking for an overview of what makes this particular "piece" (this game version) significant, The Epic Scale of the Crusade
: The "o" suffix indicates a specific minor patch within the 2.0 branch, ensuring that many of the complex interactions between mythic powers and class abilities are functioning as intended. Why It Is Highly Regarded